This application claims the benefit of U.S. Provisional Application No. 60/516,698, filed Nov. 3, 2003, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a transmission type screen. More, particularly, the present invention relates to a transmission type screen including a fly-eye lens.
2. Description of the Related Art
In prior arts, as a transmission type screen for projecting an optical image from an optical engine, one in which the viewing angle luminance distribution is widened by using a fly-eye lens (or microlens) having a lens unit cell of a rotation axis object has been proposed in Japanese Patent Application Laid-Open No. 2000-131506.
Moreover, the range of an observation angle to a screen is often different between horizontal and vertical directions at the time of observation. Accordingly, U.S. Pat. No. 4,666,248 and Japanese Patent Application Laid-Open No. 2000-111708 have proposed to individually control the viewing angle luminance distribution in the horizontal and vertical directions by forming the shape of the lens unit cell to be anamorphic or to have an arbitrarily curved surface, where it is asymmetrical in the horizontal and vertical directions.
Meanwhile, although the viewing angle luminance distribution is widened by enlarging the lens power of the lens unit cell, the luminance of a screen viewed from the front decreases. Moreover, while the observation angle to a screen is supposed to have a considerably wide range in the horizontal direction, it isn't so in the vertical direction. Consequently, for the shape of the lens unit cell, there is a proper range with respect to each of the horizontal and vertical directions. In the prior arts, however, any specific shapes of a lens unit cell are not present or suggested, and there is a problem that it is not always possible to obtain a screen of which the optical characteristics are ideal with respect to each of the horizontal and vertical directions.